From d3ebc1ae4a9feee927c8fd6a6322364c2555e43d Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Sat, 14 Sep 2002 19:32:54 +0000
Subject: [PATCH] Fix portability bug in get_normal_pair (RAND_MAX !=
MAX_RANDOM_VALUE). Also try to improve readability and performance.
---
contrib/tablefunc/tablefunc.c | 34 +++++++++++++++-------------------
1 file changed, 15 insertions(+), 19 deletions(-)
diff --git a/contrib/tablefunc/tablefunc.c b/contrib/tablefunc/tablefunc.c
index 875e340c29e..f5ac0f8ee67 100644
--- a/contrib/tablefunc/tablefunc.c
+++ b/contrib/tablefunc/tablefunc.c
@@ -224,31 +224,27 @@ get_normal_pair(float8 *x1, float8 *x2)
v2,
s;
- for (;;)
+ do
{
- u1 = (float8) random() / (float8) RAND_MAX;
- u2 = (float8) random() / (float8) RAND_MAX;
+ u1 = (float8) random() / (float8) MAX_RANDOM_VALUE;
+ u2 = (float8) random() / (float8) MAX_RANDOM_VALUE;
v1 = (2.0 * u1) - 1.0;
v2 = (2.0 * u2) - 1.0;
- s = pow(v1, 2) + pow(v2, 2);
+ s = v1 * v1 + v2 * v2;
+ } while (s >= 1.0);
- if (s >= 1.0)
- continue;
-
- if (s == 0)
- {
- *x1 = 0;
- *x2 = 0;
- }
- else
- {
- *x1 = v1 * sqrt((-2.0 * log(s)) / s);
- *x2 = v2 * sqrt((-2.0 * log(s)) / s);
- }
-
- return;
+ if (s == 0)
+ {
+ *x1 = 0;
+ *x2 = 0;
+ }
+ else
+ {
+ s = sqrt((-2.0 * log(s)) / s);
+ *x1 = v1 * s;
+ *x2 = v2 * s;
}
}
--
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